The present invention relates to an electric ignition system which can be used, for example, as an ignition for an air bag gas generator.
Known electric ignitions typically include an ignitor primary charge which includes an insulating base containing an electric plug, an ignitor and a primary ignition powder. In known arrangements, the ignitor is arranged on the insulating base and the primary ignition powder completely surrounds the ignitor. The primary ignition powder is enclosed by a sleeve of plastic which is placed or plugged on the base. A metal sleeve which includes a window or opening for axial ignition propagation is placed over the plastic sleeve and fastened by gluing, crimping or sealing.
A number of problems occur in the production of known ignitor primary charges of the type described above. For instance, when the metal sleeve is slipped over the plastic sleeve and glued, crimped or sealed, mechanical and thermal stresses occur which can damage the base or otherwise alter the structure of the ignitor primary charge. Such changes in the structure of the ignitor primary charge can allow moisture to intrude from the electric plug into the ignitor along the electric conductors thus impairing operation. Moreover, the insulating base may be misaligned or fastened in the metal sleeve askew such that the ignitor primary charge is not properly sealed, i.e., leaky. Finally, the known constructions are not particularly well suited for automatic manufacture and testing. Specifically, the metal sleeve is rotatable with respect to the base and there are no connecting surfaces or flanges for assembly of the ignitor charge plug in equipment.